Under Armour, a company best known for workout clothes, has been quietly starting to dominate fitness tech. And on Tuesday, it launched its most ambitious move yet with partner HTC, a product called HealthBox.

HealthBox combines a fitness tracker with a heart-rate strap and a smart scale in a $400 bundle. All of these are intended to be used with UA's updated Record smartphone app, which can also work with other fitness trackers.

Record is an app that tracks and analyzes fitness and activity data, combined with a social network where you can talk training etc. with other athletes.

The fitness tracker is essentially HTC's Grip, come back from the dead. The HTC Grip was announced at Mobile World Congress 2015, a $199 sleep and step-tracker with touch display, that HTC never wound up bringing to market. It is now called UA Band and this version has something the old Grip lacked, a heart-rate sensor of sorts.

But, as wrist sensors are not nearly as accurate as chest straps, the bundle includes a Bluetooth chest strap for doing more serious training. It can be used with the band or connect directly to the Record app on your iPhone or Android.

The scale measures weight, body fat and can hold weight goals for up to 8 users.

Pricey setup

One complaint: $400 is pricey for this setup, given you can get a modest step/sleep tracker for less than $100 these days, a smart scale for under $150 and a Bluetooth chest strap for about $60.

Still, HealthBox is another step in the fit-tech ambitions of Under Armour, who bought the Map My Fitness app company in 2013 for $150 million, and then spent another half a billion in 2015 to buy fitness app companies. It bought running/distance app Endomondo for $85 million and food/exercise tracking app MyFitnessPal in 2015 for $475 million.

More and more, if you use your smartphone to track fitness goals, you run into Under Armour.

Gizmodo's Darren Orfa has a review of the the HealthBox band and the Record app. He thinks HTC and UA get "a few things very, very right." One of them is amazing battery life. The band can hold a charge for up to 5 days and recharge itself in about 15 minutes. For comparison, we have a Fitbit Surge and can testify that it holds a charge for a good 2+ days and charges within 30 minutes.